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Miller" , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-riscv@lists.infradead.org, loongarch@lists.linux.dev, sparclinux@vger.kernel.org, Alexandre Ghiti , Albert Ou , WANG Xuerui , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko Subject: Re: [PATCH v3 1/5] mm/sparse-vmemmap: provide generic vmemmap_set_pmd() and vmemmap_check_pmd() Message-ID: References: <20260601084845.3792171-1-songmuchun@bytedance.com> <20260601084845.3792171-2-songmuchun@bytedance.com> <0D4AF42F-37C5-4A76-9703-44ACC6374C48@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <0D4AF42F-37C5-4A76-9703-44ACC6374C48@linux.dev> X-Rspamd-Queue-Id: CDEBD1A0009 X-Stat-Signature: 8bbty1jsfeuoxmm78gf83tnyt7d4fjpp X-Rspam-User: X-Rspamd-Server: rspam12 X-HE-Tag: 1780375233-602185 X-HE-Meta: U2FsdGVkX19jSbtFpQIYiIHQGWgT2LugwdrsIx640p6ysNvhPM6loVVaYHb1140G/UF4FquR6axbpQG76xlsa0GKALNNrad10LARSqdkNQ5T7b1vazrJRoQPSe88kQQdjw292SoJ/PfEuG+/7Hn3a4g0d+5dD8uqDjNvNSRW1FO4EuYWHnMUNvPrKjrSBK0M17xfMxxaI7BDzjJiZ8bC/5HJSulfoI5MzkyECsKKqM1HeZ5zG9jWJw7eb+7vzb4ZFEAP2j41KgvxUqfOnSIeYdiBQx1ZugPAhTtAfhV+vPQ269R8E0J9AeyB/oVkM5KQuEtnIf1fkRBDT0p5bVUGjvPAsWpWW0LHBJILL4Lr+KO3P9D3f8K7Lq3CgMq9vZDsPNj4FZBMu9wblaskfOYxbK2N5AfUoOTJtuMg513KwMLCDXJLePWnNqMwOtnI1d2ybISPQSrCC9g9JoHAFnH5ggjwtrrbo7/NeE9BGVBdgxj0bzmw6SBHvUVhJYg7tMbxsgHLwTc0OYf9wYUKAhszRU3j5GcWn9OETLRVGPlpe5oUzaaUtiRb8mX9r6XcnswV1xxaScMyWP/4lJXAJTH5qA1q5q+OdP+4QK1rLY//juiHMP7KJ0MHbA/UvQ3rNFdEIFxF4gWYwAonnIq3bmr7o/JDbBYPOY1JA3IJ6hR9UtE2El+wkwpryuKxpWS8Wpz9nvaf9iFAwu4fWqIrvFdg3HswrHzGyiY927VuzmixnmNo7IO7Pe6fB+kj5Uts+iwlGY3+tjhffa3JJbt3bwU6/MhilU1QFOCbam1gx2M0VC23GmEhxTjBWNdzcWkQ5/KsD+95CuXx30ggbTsDEZni1I8RSP/cX6bOhq63cOARvdwzCayEvt1n5E3ezeT/NcdNK5H9pQxizwURC4HfhH9osOIHqf+GZdqDyaGfY2uGGHpimmPCeXFZp1HffvMtyQ45BhUStt8/sq8wepnEpa5 q7kG+etU 2V7UN+cdq8pQCv11We1U5Ah+IIVkE4yYfhwjZBDd1AEAzAyaKwl/Y0d+BUm3u5f4HGWoMp5rfSN8F6d8N8pV+WqfFKcwLW2KJlhhDiTAf5c/r6WCdfz+kCJAoSkKynsgkjhSOeLVhuwcCHJoetN1lelbC+CtCkGFotWpXGr4XJ31pD9yX2eWeQGGIULmvMqtPpD/9S324UNl4YsRXuOQR2Ex6lhu+c9WSAvQLh3HOyiE65fWDo6XUPQ2Dq/uSMiludLO9GRrBwTBMihVI9/5xxtmAB2o77SZEQqRuEyONnac2ng14Vica2tAB4g== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Jun 01, 2026 at 08:37:42PM +0800, Muchun Song wrote: > > > > On Jun 1, 2026, at 20:22, David Hildenbrand (Arm) wrote: > > > > On 6/1/26 10:48, Muchun Song wrote: > >> The two weak functions are currently no-ops on every architecture, > >> forcing each platform that needs them to duplicate the same handful > >> of lines. Provide a generic implementation: > >> > >> - vmemmap_set_pmd() simply sets a huge PMD with PAGE_KERNEL protection. > >> > >> - vmemmap_check_pmd() verifies that the PMD is present and leaf, > >> then calls the existing vmemmap_verify() helper. > >> > >> Architectures that need special handling can continue to override the > >> weak symbols; everyone else gets the standard version for free. > >> > >> Signed-off-by: Muchun Song > >> --- > >> v2->v3: > >> - Replace BUG_ON() with WARN_ON_ONCE() in vmemmap_set_pmd() > >> --- > >> mm/sparse-vmemmap.c | 7 ++++++- > >> 1 file changed, 6 insertions(+), 1 deletion(-) > >> > >> diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c > >> index 112ccf9c71ca..99e2be39671b 100644 > >> --- a/mm/sparse-vmemmap.c > >> +++ b/mm/sparse-vmemmap.c > >> @@ -386,12 +386,17 @@ int __meminit vmemmap_populate_hvo(unsigned long addr, unsigned long end, > >> void __weak __meminit vmemmap_set_pmd(pmd_t *pmd, void *p, int node, > >> unsigned long addr, unsigned long next) > >> { > >> + WARN_ON_ONCE(!pmd_set_huge(pmd, virt_to_phys(p), PAGE_KERNEL)); > > > > > > Not sure if a VM_WARN_ON_ONCE() would be appropriate. (then, we have to move the > > pmd_set_huge() out of the statement). > > I think it might be better to keep WARN_ON_ONCE here. This way, we can still > monitor for warnings in production while keeping the code simple. IIRC there was a discussion about this some time ago, given the fact that quite some people out there tend to have 'panic_on_warn', but then again, if we fail to set a PMD here it means something pretty nasty happened, so I am ok with that. -- Oscar Salvador SUSE Labs